Vegetable oils and fats, such as: soybean oil; cotton seed oil; palm oil; sunflower oil; rice oil; and other similar oils contain sitosterol, campesterol, stigmasterol, and various other sterols at levels generally less than 0.5 percent weight. These oils are treated by saponification, extraction, and crystallization, followed by distillation and high pressure propane extraction to concentrate the sterols.
The concentrated sterol mixture is often the by-product of commercial processes for obtaining soap during a vegetable oil deodorization process. In the first instance, soap is extracted by saponifying the sterol esters to yield the soap and the free sterols. In the vegetable oil deodorization process, the concentrated sterol mixture is obtained by steam stripping the undesirable odors generally present in, for instance, crude soybean oil. The free sterol obtained from soap processing is then conventionally separated from other components present in the sterol mixture by solvent extraction.
A variety of assorted processes have been disclosed for the recovery and purification of sterols from natural products employing evaporative and distillation techniques.
U.S. Pat. No. 4,076,700, issued Feb. 28, 1978, hereby incorporated by reference, discloses a process for the recovery of fatty and rosin acids and separating sitosterol. The process involves the separate saponification, with an alkali solution of tall oil, in a saponification vessel. The soap formed and other unsaponifiables, like sitosterol, are subsequently processed through a first, vertical, thin film evaporator to evaporate light ends and then a second, vertical, thin film evaporator to recover the sterol sitosterol.
U.S. Pat. No. 5,487,817, issued Jan. 30, 1996, hereby incorporated by reference, involves the recovery of tocopherols and sterols from vegetable sources, by the esterification of the sterols and subsequent distillation to isolate the sterols.
U.S. Pat. No. 5,646,311, issued Jul. 8, 1997, and hereby incorporated by reference, relates to the recovery of tocopherols, by distillation of fatty acid esters in a packed column, followed by wiped or thin film evaporation and then crystallization of the sterols from a solvent blend.
U.S. Pat. No. 5,658,433, issued Aug. 19, 1997, and U.S. Pat. No. 5,582,692, issued Dec. 10, 1996, both hereby incorporated by reference, concern the recovery and purification of tocopherols (vitamin E), by employing a distillation column and a rotary thin film evaporator.
It is desirable to provide a rapid, efficient, high yield, economic, solvent-free method and system for the concentration and recovery of purified, free sterols from natural fats and oils containing: free sterols; sterol esters; and combinations thereof, typically, from natural oil and fat by-product residues or distillates containing fatty acids, glycerides, and sterol esters.